Fuel cell system

Abstract

The present application relates to a fuel cell system, comprising: a fuel cell having a plurality of single cells stacked; a fuel gas supply unit configured to supply a fuel gas to a supply port of the fuel cell and to return a fuel gas discharged from a discharge port of the fuel cell to the supply port; and a control device configured to control an operation of the fuel gas supply unit. The control device is configured to perform a water discharge process for discharging residual water stored in the fuel cell from the discharge port, and repeatedly performs a first process and a second process in the water discharge process. The first process refers to supplying the fuel gas to the fuel cell until a pressure in the fuel cell reaches a predetermined threshold pressure. The second process refers to reducing the pressure in the fuel cell after the first process.

Description

Technical Field

[0001] The technology disclosed in this specification relates to fuel cell systems. Background Technology

[0002] Japanese Patent Application Publication No. 2008-10347 discloses a fuel cell system for removing residual water from a fuel cell. In this system, a compressor supplying air (i.e., oxidizing gas) to the fuel cell and a gas flow path supplying hydrogen (i.e., fuel gas) to the fuel cell are connected via a first connecting valve. When removing residual water from the gas flow path, the fuel cell system opens the first connecting valve and supplies oxidizing gas into the gas flow path via the compressor. As a result, the gas flow path is pressurized by the oxidizing gas, and the residual water is removed. Summary of the Invention

[0003] In the fuel cell system described in Japanese Patent Application Publication No. 2008-10347, an oxidizing gas is used to remove residual water from the gas flow path that should be supplied with fuel gas during power generation. Therefore, power generation by the fuel cell is stopped during the removal of residual water. This specification provides a technique that allows for the removal of residual water even during power generation by the fuel cell.

[0004] This specification discloses a fuel cell system. The fuel cell system includes: a fuel cell having multiple stacked individual cells; a fuel gas supply unit configured to supply fuel gas to a supply port of the fuel cell; and a control device configured to control the operation of the fuel gas supply unit. The fuel gas supply unit has a return path configured to return the fuel gas discharged from the outlet of the fuel cell to the supply port, and a gas-liquid separator disposed in the return path. The control device is configured to perform a drainage process to discharge residual water accumulated in the fuel cell from the outlet. In the drainage process, a first process and a second process are repeatedly performed. The first process involves supplying fuel gas to the fuel cell until the pressure inside the fuel cell reaches a predetermined threshold pressure. The second process involves reducing the pressure inside the fuel cell after the first process.

[0005] In the aforementioned fuel cell system, during the first stage of drainage treatment, fuel gas is supplied to the fuel cell via a fuel gas supply unit to pressurize the fuel cell until the pressure inside the fuel cell reaches a predetermined threshold pressure. As a result, residual water inside the fuel cell is discharged from the outlet along with the fuel gas and separated from the fuel gas in a gas-liquid separator. Consequently, the separated fuel gas flows back to the fuel cell's supply port, while the separated residual water is discharged to the outside. If the pressure inside the fuel cell reaches the predetermined threshold pressure, fuel gas is difficult to enter the fuel cell. Therefore, in the second stage performed after the first stage, the pressure inside the fuel cell is reduced. This allows the fuel gas supply unit to supply a large amount of fuel gas to the fuel cell again. Thus, the fuel cell system disclosed in this specification utilizes fuel gas to remove residual water from the fuel cell. Therefore, even during fuel cell power generation, the fuel cell system can remove residual water.

[0006] In one embodiment of this technology, the fuel gas supply unit may include a discharge valve connected to the gas-liquid separator. In this case, the control device may be configured to keep the discharge valve closed during the first process and to reduce the pressure inside the fuel cell by opening the discharge valve during the second process.

[0007] In one embodiment of this technology, the control device may be configured to reduce the pressure inside the fuel cell by increasing the power generation of the fuel cell compared to the first process in the second process.

[0008] In one embodiment of this technology, the fuel cell may further include: a manifold that connects the outlet to the plurality of individual cells; and a bypass pipe that extends from the manifold to the outlet.

[0009] In one embodiment of this technology, the control device may be configured to change the flow rate of the fuel gas supplied to the fuel cell according to the tilt of the fuel cell relative to the horizontal direction in the first process.

[0010] In one embodiment of this technology, the control device may be configured to perform the drainage process when the actual operating performance of the fuel cell exceeds a predetermined threshold performance.

[0011] The details of the technology disclosed in this specification and further improvements will be described in the following "Detailed Description". Attached Figure Description

[0012] Hereinafter, the features, advantages, technical and industrial importance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which the same reference numerals denote the same constituent elements, wherein:

[0013] Figure 1 A block diagram illustrating the fuel cell system of the first embodiment.

[0014] Figure 2 This shows a side view of the fuel cell.

[0015] Figure 3 This indicates the changes in each value when drainage treatment is performed by the control device of the first embodiment.

[0016] Figure 4 A flowchart illustrating the processing performed by the control device in the first embodiment.

[0017] Figure 5 This indicates the changes in each value when drainage treatment is performed by the control device of the second embodiment.

[0018] Figure 6 A flowchart illustrating the processing performed by the control device in the second embodiment. Detailed Implementation

[0019] In one embodiment of this technology, the fuel gas supply unit may include a discharge valve connected to the gas-liquid separator. In this case, the control device may be configured to keep the discharge valve closed during the first process and to reduce the pressure inside the fuel cell by opening the discharge valve during the second process. With this configuration, by repeatedly opening and closing the discharge valve in a short period of time, a large amount of fuel gas can be supplied to the fuel cell in a short time. As a result, even in situations where it is difficult to discharge residual water, such as when the fuel cell is tilted relative to the horizontal direction, a large amount of fuel gas can be used to discharge residual water.

[0020] In one embodiment of this technology, the control device can be configured to reduce the pressure within the fuel cell by increasing the power generation of the fuel cell compared to the first process during the second process. With this configuration, since the fuel gas used to discharge residual water is utilized in power generation, residual water can be discharged without wasting fuel gas.

[0021] In one embodiment of this technology, the fuel cell may further include: a manifold connecting the outlet to the plurality of individual cells; and a bypass pipe extending from the manifold to the outlet. With this structure, the bypass pipe is prone to localized negative pressure due to the discharge of fuel gas from the outlet. Therefore, residual water can be discharged from the outlet via the bypass pipe.

[0022] In one embodiment of this technology, the control device can be configured to change the flow rate of the fuel gas supplied to the fuel cell according to the tilt of the fuel cell relative to the horizontal direction during the first process. When the fuel cell is tilted relative to the horizontal direction, even when fuel gas is supplied to the fuel cell, residual water may sometimes be unable to be discharged from the fuel cell. With this configuration, by changing the flow rate of the fuel gas according to the tilt, residual water can be discharged from the fuel cell even when the fuel cell is tilted relative to the horizontal direction.

[0023] In one embodiment of this technology, the control device may be configured to perform the drainage process when the actual operating performance of the fuel cell exceeds a predetermined threshold performance. However, in other embodiments, the drainage process may be performed, for example, at predetermined intervals.

[0024] (Example)

[0025] The fuel cell system of an embodiment will be described with reference to the accompanying drawings. Figure 1 This is a block diagram illustrating a fuel cell system 100 according to an embodiment. The fuel cell system 100 is mounted on an electric vehicle (not shown). The fuel cell system 100 includes a fuel cell 20. The fuel cell system 100 is a system for generating electricity using the fuel cell 20. The fuel cell system 100 supplies the generated electricity to the motor (not shown) of the electric vehicle. Alternatively, the fuel cell system 100 uses the generated electricity to charge the battery (not shown) of the electric vehicle.

[0026] The fuel cell 20 includes: an anode supply port 22a for taking in fuel gas (i.e., hydrogen); a cathode supply port 22k for taking in oxidizing gas (i.e., air); and multiple individual cells 26 (see reference). Figure 2 The fuel cell 20 generates electricity by chemically reacting hydrogen gas taken from the anode supply port 22a with oxygen from the air taken from the cathode supply port 22k in multiple individual cells 26. Since the chemical reactions that occur during the power generation of the fuel cell 20 are known, detailed descriptions are omitted.

[0027] In addition to the fuel cell 20, the fuel cell system 100 also includes a fuel gas supply unit 10, an oxidizing gas supply unit 30, and a control device 40. The fuel gas supply unit 10 includes a hydrogen tank 1, a pressure reducing valve 2, a supply pipe 3, a medium-pressure side pressure sensor 4, an injector 6, an ejector 8, a return pipe (return path) 5, a low-pressure side pressure sensor 12, a discharge pipe 7, a gas-liquid separator 14, an exhaust drain valve 16, a pump 18, and an exhaust drain pipe 9. The fuel gas supply unit 10 is used to supply hydrogen stored in the hydrogen tank 1 to the fuel cell 20. The hydrogen tank 1 is connected to the anode supply port 22a of the fuel cell 20 via the supply pipe 3. Thus, hydrogen in the hydrogen tank 1 is supplied to the fuel cell 20 via the supply pipe 3. Figure 1 For ease of understanding, points (point groups) are recorded in pipes 3, 5, and 7 of the hydrogen supply circulation.

[0028] A medium-pressure side pressure sensor 4, a pressure reducing valve 2, an injector 6, an ejector 8, and a low-pressure side pressure sensor 12 are connected to the supply pipe 3. The pressure reducing valve 2 reduces the high-pressure hydrogen in the hydrogen tank 1 to a specified pressure. The medium-pressure side pressure sensor 4 detects the pressure after pressure reduction by the pressure reducing valve 2. The injector 6 is a solenoid valve that adjusts the amount of hydrogen supplied to the ejector 8. The wider the injector 6 is opened, the greater its output, and the greater the amount of hydrogen supplied to the ejector 8. The ejector 8 uses the pressure of the hydrogen supplied from the injector 6 to draw hydrogen from the return pipe 5. The low-pressure side pressure sensor 12 detects the pressure of the hydrogen supplied from the ejector 8 to the fuel cell 20. That is, the low-pressure side pressure sensor 12 detects the pressure inside the fuel cell 20.

[0029] The exhaust pipe 7 of the fuel gas supply unit 10 is connected to the anode outlet 24a of the fuel cell 20. The exhaust gas discharged from the anode outlet 24a flows into the gas-liquid separator 14 via the exhaust pipe 7. Here, the exhaust gas includes the hydrogen remaining from the aforementioned chemical reaction in the fuel cell 20.

[0030] The gas-liquid separator 14 separates the exhaust gas discharged from the anode outlet 24a into hydrogen and impurities. For example, the gas-liquid separator 14 separates the exhaust gas within itself into hydrogen, nitrogen, and water. Nitrogen, for example, is the nitrogen contained in the air supplied to the cathode supply port 22k that passes through the electrolyte membranes (not shown) of the multiple single cells 26 to reach the anode side. The pump 18 supplies the hydrogen separated from the exhaust gas by the gas-liquid separator 14 to the ejector 8 via the return pipe 5. Thus, the hydrogen is supplied again to the anode supply port 22a of the fuel cell 20 via the ejector 8. In this way, the fuel gas supply unit 10 recirculates the hydrogen contained in the exhaust gas (i.e., fuel gas). Furthermore, in a modified example, the fuel gas supply unit 10 may not include the pump 18. In this case, the hydrogen in the return pipe 5 can be supplied to the ejector 8 by the negative pressure generated in the ejector 8.

[0031] The gas-liquid separator 14 is connected to the fuel cell 20 via the discharge pipe 7. The exhaust drain valve 16 is connected to the fuel cell 20 via the gas-liquid separator 14 and the discharge pipe 7. When the exhaust drain valve 16 is opened, impurities such as nitrogen separated from the exhaust gas by the gas-liquid separator 14 are discharged to the exhaust drain pipe 9.

[0032] Oxidizing gas supply unit 30 supplies air (oxygen) to fuel cell 20. Oxidizing gas supply unit 30 includes compressor 32, supply pipe 33, bypass pipe 35, discharge pipe 37, and valves 34, 36, and 38. Compressor 32 compresses external air and supplies it to the cathode supply port 22k of fuel cell 20 via supply pipe 33. Discharge pipe 37 is connected to cathode discharge port 24k. Bypass pipe 35 connects supply pipe 33 and discharge pipe 37 via valve 38. Valves 34 and 36 are so-called pressure regulating valves, used to adjust the pressure of the air supplied to fuel cell 20.

[0033] The control unit 40 is a computer with a CPU and memory. The control unit 40 controls each unit 10 and 30 based on driving information such as the accelerator opening and speed of the fuel cell vehicle. As a result, the fuel cell 20 generates electricity based on the driving information.

[0034] Reference Figure 2 The structure of the fuel cell 20 will be described in detail below. In addition to multiple individual cells 26, the fuel cell 20 also includes a housing 21, a supply-side manifold 23, an exhaust-side manifold 27, and a bypass tube 29. The housing 21 has a rectangular shape and houses the multiple individual cells 26. The multiple individual cells 26 are constructed by stacking each individual cell 26 along the length of the housing 21. An anode supply port 22a and an anode exhaust port 24a are arranged on one side of the housing 21 along its length. Hereinafter, for ease of understanding, one side of the fuel cell 20 along its length will sometimes be referred to as the front side and the other side as the back side.

[0035] The anode supply port 22a is located above the anode discharge port 24a. The supply pipe 3 is connected to the supply-side manifold 23 via the anode supply port 22a. The supply-side manifold 23 is the space connecting the supply pipe 3 to multiple individual cells 26. The supply-side manifold 23 is open to the outside of the housing 21 on the front side of the fuel cell 20 and closed by the housing 21 on the rear side of the fuel cell 20. Hydrogen gas in the supply pipe 3 is supplied to the multiple individual cells 26 via the supply-side manifold 23.

[0036] Similarly, the exhaust pipe 7 is connected to the exhaust manifold 27 via the anode outlet 24a. The exhaust manifold 27 is the space that connects the exhaust pipe 7 to the multiple individual cells 26. The exhaust manifold 27 is open to the outside of the housing 21 on the front side of the fuel cell 20 and is closed by the housing 21 on the rear side of the fuel cell 20. The exhaust gas passing through the multiple individual cells 26 is discharged to the exhaust pipe 7 via the anode outlet 24a.

[0037] The bypass pipe 29 is cylindrical and open at both ends. It is positioned on the bottom surface of the discharge manifold 27. The bypass pipe 29 extends along the bottom surface of the discharge manifold 27 to the anode outlet 24a. The rear end of the bypass pipe 29 is located at the rear end of the discharge manifold 27. The cross-sectional area of ​​the bypass pipe 29 is smaller than that of the discharge manifold 27. Therefore, the flow velocity of the exhaust gas through the bypass pipe 29 is faster than that through the discharge manifold 27. Within the bypass pipe 29, manifold pressure loss and dynamic pressure differential are generated, creating a pressure difference between the inlet and outlet of the bypass pipe 29. Therefore, the bypass pipe 29 can discharge residual water W from the anode outlet 24a to the outside of the fuel cell 20 in a relatively short time.

[0038] The exhaust manifold 27 extends along the bottom surface of the housing 21 of the fuel cell 20 from the rear side of the fuel cell 20 to the front side. Therefore, water generated through chemical reactions can easily remain in the exhaust manifold 27. This is particularly problematic when a fuel cell vehicle equipped with the fuel cell system 100 is traveling on an inclined slope, with the fuel cell 20 tilted at an angle A1 relative to the ground GL. Figure 2 As shown, residual water W tends to accumulate at the rear end of the exhaust manifold 27 of the fuel cell 20. The drainage process performed by the control device 40 to discharge the residual water W from the fuel cell 20 will be described below.

[0039] Reference Figure 3 as well as Figure 4 The drainage process performed by the control device 40 of the first embodiment will be described. Figure 3The graph shows the changes in pressure P within the fuel cell 20 over time (Graph A), the changes in the state of the exhaust / drain valve 16 (Graph B), and the changes in the flow rate V of hydrogen supplied to the fuel cell 20 (Graph C). In Graph A, the solid line represents the pressure command value Pd within the fuel cell 20 sent by the control device 40 to the fuel gas supply unit 10, and the dashed line represents the low-pressure side pressure sensor 12 (see Figure C). Figure 1 The actual measured value Pr (i.e., the pressure value P inside the fuel cell 20).

[0040] The control device performs the first process during the first period T1, and then performs the second process during the second period T2. For example... Figure 3 As shown by the solid line in Chart A, in the first process, the control device 40 sends a threshold pressure value P2 as a pressure command value Pd to the fuel gas supply unit 10 during the first period T1. Specifically, in the first process, the control device 40 controls the pressure reducing valve 2, the injector 6, and the pump 18 of the fuel gas supply unit 10 to increase the flow rate V of the fuel gas supplied to the fuel cell 20 until the pressure value P inside the fuel cell 20 reaches the threshold pressure value P2. Here, the threshold pressure value P2 is the pressure value used to determine whether the fuel cell 20 is in a state where fuel gas can be supplied, and it can be calculated based on the size of the fuel cell 20, the size of each pipe in the fuel gas supply unit 10, etc. The result is as follows: Figure 3 As shown in Figure C, during the first period T1, the flow rate V of hydrogen supplied to the fuel cell 20 increases from the normal flow rate V1 to the drainage flow rate V2.

[0041] Therefore, hydrogen permeates the first period T1 through the manifolds 23 and 27 within the fuel cell 20. At this time, residual water W (referring to...) accumulates in the exhaust manifold 27. Figure 2 It is discharged to the discharge pipe 7 via the anode outlet 24a.

[0042] In addition, such as Figure 3 As shown in Figure B, in the first process, the control device 40 keeps the exhaust / drain valve 16 closed throughout the first period T1. In other words, during the first period T1, fuel gas is supplied to the fuel cell 20 while the supply pipe 3, fuel cell 20, exhaust pipe 7, and return pipe 5 are sealed. Therefore, as Figure 3 As shown in the dashed graph of Chart A, during the first period T1, the actual pressure value P inside the fuel cell 20 increases from the normal pressure value P1 to the threshold pressure value P2.

[0043] When the pressure value P inside the fuel cell 20 reaches the threshold pressure value P2, the control device 40 begins the second process. During the second process, the control device 40 opens the exhaust / drain valve 16 throughout the second period T2. Additionally, during the second period T2, as... Figure 3 As shown in Figure A, the control device 40 sends a normal pressure value P1, which is lower than the threshold pressure value P2, as a pressure command value Pd to the fuel gas supply unit 10. As a result, during the second period T2, as... Figure 3 As shown in Figure C, the flow rate V of the fuel gas supplied to the fuel cell 20 decreases from the drainage flow rate V2 to the normal flow rate V1. Furthermore, as... Figure 3 As shown in the dashed graph of Chart A, during the second period T2, the pressure value P inside the fuel cell 20 decreases from the threshold pressure value P2 to the normal pressure value P1.

[0044] Thus, in the second process, the pressure P inside the fuel cell 20 decreases to the normal pressure P1. As a result, the control device 40 can supply hydrogen to the fuel cell 20 by repeating the first process. That is, the residual water W inside the fuel cell 20 is discharged again. In this way, by alternately repeating the first and second processes, the control device 40 can discharge the residual water W accumulated in the discharge manifold 27 of the fuel cell 20 from the anode outlet 24a.

[0045] Next, refer to Figure 4 The drainage process performed by the control device 40 will be described. The control device 40 performs, for example, the drainage process while an electric vehicle is in motion. Figure 4 The processing. Therefore, at the beginning Figure 4 During the drainage process, the control device 40 sends the normal pressure value P1 as a pressure command value Pd to the fuel gas supply unit 10, and the pressure reducing valve 2 and the injector 6 are opened (see reference). Figure 1 Hydrogen gas at a flow rate of V1 is typically supplied to fuel cell 20. That is, fuel cell 20 is generating electricity at the moment when control device 40 begins drainage treatment.

[0046] In step S2, the control device 40 determines whether the actual operating performance of the fuel cell 20 is above a threshold performance. Specifically, the control device 40 determines whether the electrical power generated by the fuel cell 20 is above a threshold electrical power. The residual water W accumulated in the fuel cell 20 (refer to...) Figure 2 The amount of residual water W is proportional to the power output of fuel cell 20. Therefore, if the electrical power output of fuel cell 20 is less than the threshold electrical power, it can be inferred that the amount of residual water W is low. In this case, control device 40 determines that the actual operating performance of fuel cell 20 has not reached the threshold actual performance (S2: No), and executes step S2 again. That is, control device 40 repeatedly performs step S2 until the electrical power output of fuel cell 20 reaches or exceeds the threshold electrical power (i.e., until the amount of residual water W is inferred to exceed the specified amount).

[0047] If the electrical power output is above the threshold electrical power, the control device 40 determines that the actual operating performance of the fuel cell 20 is above the threshold actual performance (S2: Yes), and proceeds to step S4 to begin the first process. In step S4, as referred to... Figure 3 As illustrated in Figure A, the control unit 40 sends the threshold pressure value P2 as a pressure command value Pd to the fuel gas supply unit 10. Subsequently, the outputs of the injector 6 and pump 18 are increased. As a result, the flow rate V of hydrogen supplied to the fuel cell 20 increases to the discharge flow rate V2.

[0048] Furthermore, as previously described, the control device 40 is receiving driving information from the electric vehicle. Therefore, for example, when the electric vehicle is traveling on an incline, the control device 40 can estimate the angle A1 of the incline relative to the horizontal direction (see reference) based on information such as motor torque, speed, and driving speed. Figure 2 In steps S2 and S4, the control device 40 adjusts the threshold pressure value P2 based on the estimated angle A1. Specifically, the larger the angle A1, the greater the threshold pressure value P2. Therefore, the larger the angle A1, the greater the output of the injector 6, and the more hydrogen is supplied to the fuel cell 20. This allows residual water in the tilted fuel cell 20 to be discharged.

[0049] In step S6, the control device 40 calculates the amount of water removed W2 based on the output of the injector 6 determined in step S4 and the elapsed time. Next, in step S8, the control device 40 compares the amount of residual water W1 calculated based on the actual operating results in step S2 with the amount of water removed W2 calculated in step S6. Here, the amount of residual water W1 is a presumed amount of residual water W remaining in the fuel cell 20, calculated based on the actual operating results. If all the residual water W in the amount of residual water W1 is removed, it can be presumed that the drainage within the fuel cell 20 is complete. Therefore, if the amount of water removed W2 is greater than the amount of residual water W1 (S8: Yes), the control device 40 determines that the drainage of residual water W is complete and proceeds to step S10, sending the normal operating pressure value P1 as a pressure command value Pd to the fuel gas supply unit 10. As a result, the output of the injector 6 decreases. Consequently, the flow rate V of hydrogen supplied to the fuel cell 20 decreases to the normal operating flow rate V1. Then, the control device 40 ends the drainage process.

[0050] On the other hand, if the amount of water removed W2 is less than the amount of residual water W1 (S8: No), the control device 40 determines that residual water W still exists in the fuel cell 20, that is, it determines that the drainage of the fuel cell 20 is not complete. In step S12, the pressure value P of the fuel cell 20 is compared with the threshold pressure value P2. If the pressure value P does not reach the threshold pressure value P2 (S12: No), the control device 40 returns to the process of step S6 and estimates the amount of water removed W2. The control device 40 executes the process of step S8 again and compares the amount of residual water W1 with the amount of water removed W2. In this case, the amount of residual water W1 in the fuel cell 20 is reduced due to the process of step S4. The control device 40 repeats the processes of steps S6 and S8 until the amount of residual water W1 is lower than the specified threshold water amount, or the pressure value P reaches the threshold pressure value P2. Here, the threshold water amount is the amount of residual water W that can be determined to be acceptable even if there is residual water W remaining in the fuel cell 20. The threshold water volume is calculated based on the size of the fuel cell 20, its power generation, and other factors.

[0051] When the pressure value P reaches the threshold pressure value P2 (S12: Yes), the control device 40 proceeds to step S14, starting the second process. In step S14, as referred to... Figure 3 As illustrated in Figure A, the control device 40 sends the normal pressure value P1 as a pressure command value Pd to the fuel gas supply unit 10. Therefore, as shown in reference... Figure 3 As illustrated in Figure C, the flow rate V of hydrogen supplied to fuel cell 20 is reduced to the normal flow rate V1. Furthermore, in step S16, as referred to... Figure 3 As illustrated in Chart B, control device 40 opens exhaust drain valve 16. This reduces the pressure P within fuel cell 20.

[0052] Next, in step S18, the control device 40 determines whether the pressure value P has decreased to the normal pressure value P1. If the pressure value P has not decreased to the normal pressure value P1 (S18: No), the control device 40 returns to the process of step S18 to monitor whether the pressure value P has decreased to the normal pressure value P1. That is, the control device 40 repeatedly performs the process of step S18 until the pressure value P decreases to the normal pressure value P1.

[0053] If the pressure value P drops to the normal pressure value P1 (S18: Yes), the control device 40 executes the process of step S4 again, sending the threshold pressure value P2 as a pressure command value Pd to the fuel gas supply unit 10. That is, if the pressure value P drops to the normal pressure value P1, the control device 40 executes the first process again.

[0054] Thus, when the pressure value P reaches the threshold pressure value P2 in the first process, the control device 40 of this embodiment reduces the pressure value P inside the fuel cell 20 by opening the exhaust drain valve 16 in the second process. Therefore, the pressure value P inside the fuel cell 20 can be reduced relatively easily. As a result, a large amount of accumulated residual water W can be discharged in a relatively short time.

[0055] (Second Implementation)

[0056] Reference Figure 5 as well as Figure 6 The fuel cell system 100 of the second embodiment will now be described. Compared with the fuel cell system 100 of the first embodiment, the fuel cell system 100 of the second embodiment performs a different process in the second process, but has the same structure in all other respects.

[0057] Figure 5 The chart shows the changes in pressure P within fuel cell 20 over time (Chart A), the changes in power generation current I of fuel cell 20 (Chart B), and the changes in hydrogen flow rate V supplied to fuel cell 20 (Chart C). Figure 5 Chart A and Figure 3 Similarly, in Chart A, Figure 5 Chart C and Figure 3 Similarly, in Figure C, the control device 40 of the second embodiment increases the power generation current value I of the fuel cell 20 from the normal current value I1 to the drainage current value I2 during the second period T2. During the second period T2, the control device 40 controls the oxidizing gas supply unit 30 to supply oxygen corresponding to the drainage current value I2. As a result, the fuel gas in the fuel cell 20 is consumed for power generation. Figure 5 As shown in Figure A, during the second period T2, the pressure value P decreases to the normal pressure value P1. Even if the pressure value P inside the fuel cell 20 increases due to the first treatment, the fuel cell system 100 of this embodiment can supply hydrogen to the fuel cell 20 again.

[0058] Reference Figure 6 The processing performed by the control device 40 in this embodiment will be described. Figure 6 In terms of the processing in step S26 and Figure 5 Step S16 is different, but the other points are the same. Figure 5Similarly, when the pressure value P reaches the threshold pressure value P2 (S12: Yes), after the control device 40 sends the normal pressure value P1 as a pressure command value Pd to the fuel gas supply unit 10 in step S14 to start the second process, it proceeds to the process in step S26. In step S26, the control device 40 increases the power generation current value I of the fuel cell 20 from the normal current value I1 to the drainage current value I2. Thus, as Figure 5 As shown in Chart A, the pressure value P inside fuel cell 20 decreases.

[0059] Thus, when the pressure value P reaches the threshold pressure value P2, the control device 40 of this embodiment reduces the pressure value P by increasing the power generation current value I of the fuel cell 20 from the normal current value I1 to the drainage current value I2. The increased power generation is used to charge the battery of the electric vehicle (not shown). Therefore, residual water W can be discharged without wasting hydrogen.

[0060] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely illustrative and do not limit the technical solutions claimed in this application. The technology described in the technical solutions claimed in this application includes technical solutions obtained by various modifications and alterations to the specific examples described above. The following are examples of modifications to the above-described embodiments.

[0061] (Variation Example 1)

[0062] The control device 40 of the first embodiment described above performs drainage processing during power generation by the fuel cell 20. However, the control device 40 of this modified embodiment can also perform drainage processing during periods when the fuel cell 20 is not generating electricity. In this case, for example, in... Figure 4 In step S16, the injector 6 can be shut off.

[0063] (Variation Example 2)

[0064] In the first process, the control device 40 can supply hydrogen to the fuel cell 20 by changing only the output of the pump 18 without changing the output of the injector 6. Furthermore, in a further variation, in the first process, the control device 40 can supply hydrogen to the fuel cell 20 by changing only the output of the injector 6 without changing the output of the pump 18.

[0065] (Variation Example 3)

[0066] In step S6, the control device 40 of the first embodiment can calculate the amount of water removed W2 based on the detection value of the medium-pressure side pressure sensor 4 and the time when the ejector 6 was opened.

[0067] (Variation Example 4)

[0068] In the processing of step S18, the control device 40 of the first embodiment can, instead of comparing the pressure value P with the normal pressure value P1, infer the cumulative exhaust volume value based on the rate of decrease of the detection value of the low-pressure side pressure sensor 12, and restart the first processing if the cumulative exhaust volume value exceeds a predetermined threshold.

[0069] (Variation Example 5)

[0070] In the second embodiment, the control device 40 can replace the comparison between the pressure value P and the normal pressure value P1 in the processing of step S18, and restart the first processing if the power generation current value exceeds the predetermined threshold power generation current value.

[0071] (Variation Example 6)

[0072] The fuel cell 20 may not have a bypass pipe 29.

[0073] (Variation Example 7)

[0074] In step S4, the control device 40 of the first embodiment can change the output of the injector 6 without considering the tilt angle A1 of the fuel cell 20. That is, the control device 40 of this modified example can change the hydrogen supply without considering the tilt angle A1 of the fuel cell 20.

[0075] (Variation Example 8)

[0076] In step S2, the control device 40 may initiate the drainage process without considering the actual operating performance of the fuel cell 20. The control device 40 may initiate the drainage process at predetermined intervals or according to instructions from the user.

[0077] The technical elements described in this specification or accompanying drawings, individually or in various combinations, exert their technical usefulness and are not limited to the combinations described in the technical solution at the time of application. Furthermore, the technologies illustrated in this specification or accompanying drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives is itself technically useful.

Claims

1. A fuel cell system, characterized in that, include: A fuel cell consists of multiple individual cells stacked together. A fuel gas supply unit is configured to supply fuel gas to the supply port of the fuel cell; and The control device is configured to control the operation of the fuel gas supply unit. in, The fuel gas supply unit has a return path configured to return the fuel gas discharged from the outlet of the fuel cell to the supply port, and a gas-liquid separator disposed in the return path. The control device is configured to perform a drainage process to discharge residual water accumulated in the fuel cell from the outlet, and the first and second processes are repeatedly performed in the drainage process. The first process refers to supplying fuel gas to the fuel cell until the pressure inside the fuel cell reaches a predetermined threshold pressure. The second treatment refers to reducing the pressure inside the fuel cell after the first treatment. The control device is configured to reduce the pressure within the fuel cell in the second process by increasing the power generation of the fuel cell compared to the first process.

2. The fuel cell system according to claim 1, characterized in that, The fuel gas supply unit includes a discharge valve connected to the gas-liquid separator. Furthermore, the control device is configured to keep the discharge valve closed during the first process, and to reduce the pressure inside the fuel cell by opening the discharge valve during the second process.

3. The fuel cell system according to claim 1 or 2, characterized in that, The fuel cell also features: A manifold connects the outlet to the plurality of individual cells; and A bypass pipe extends from the manifold to the outlet.

4. The fuel cell system according to claim 1 or 2, characterized in that, The control device is configured to change the flow rate of the fuel gas supplied to the fuel cell in the first process according to the tilt of the fuel cell relative to the horizontal direction.

5. The fuel cell system according to claim 1 or 2, characterized in that, The control device is configured to perform the drainage treatment if the actual operating performance of the fuel cell exceeds a predetermined threshold actual performance.

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